The mass spectrometry determination of elemental and of isotopic information are important analytical methods. The use of a mass spectrometer makes it possible to identify individual chemical elements or compounds. A significant application in this context is the determination of the isotopic ratios of individual elements in a starting substance, for example 18O/16O in water or the determination of different hydrogen isotopes. Since the variations of the isotopic ratios are minimal, extremely precise measurement apparatus and processes are required for the analysis. Therefore, importance attaches not only to the mass spectrometry itself, but also to the preparation of the chemical elements or compounds for the analysis to be carried out.
In an existing isotope analysis process, the oxygen of water is not analyzed directly. Rather, the isotopic information is transferred to carbon dioxide (CO2) by the method of equilibration. To this end, a small amount of the water to be analyzed is introduced into a vessel, as is an even smaller amount of CO2. The proportion of water is higher by a factor of about 103 than the proportion of CO2. The vessel is shaken and there is mixing of the isotopic information from the oxygen of the water and the CO2. Owing to the significantly greater proportion of water, the original isotopic information from the CO2 is virtually suppressed. The equilibrated CO2 then contains the isotopic information of the oxygen from the water and is removed directly or using a carrier gas and fed to an isotope mass spectrometer for analysis. The disadvantage of this system is the necessary provision of the vessels for equilibrating water and CO2, and also the residence time in the vessels required therefor. This is disadvantageous, especially in the context of relatively large sample sizes.
In this process, the CO2 added to the water has the function of a reagent substance. After the equilibration, the gaseous CO2 may be referred to as a reaction product, and the water as a residual substance. The reaction product is required for the analysis.
Further processes are conceivable in which a starting substance is not directly analyzed, but rather information is passed on therefrom to a gaseous reaction product. It is important that there is a means for rapid and reliable, precise implementation.
Accordingly, it is desirable to provide a process and an apparatus which allows chemical elements or compounds to be rapidly and precisely prepared for analysis.